Phase Transformations on Aging Cu-Al-Ni β Phase Alloys

1983 ◽  
Vol 21 ◽  
Author(s):  
S. W. Husain ◽  
P. C. Clapp ◽  
M. Ahmed
Keyword(s):  
Martensitic Transformation ◽  
Phase Transformations ◽  
Parent Phase ◽  
Isothermal Kinetics ◽  
X Ray Diffraction ◽  
Subsequent Aging ◽  
X Ray ◽  
Β Phase ◽  
Transmission Electron ◽  
Equilibrium Phases

ABSTRACTThe phase transformations occurring on quenching and subsequent aging of a Cu-Al-Ni β phase alloy have been studied using transmission electron microscopy, x-ray diffraction and optical microscopy. Quenching produces an ordered solid solution, β1, based on the DO3 structure of Cu3A1. X-ray and electron diffraction show satellite diffraction peaks. On aging, these satellite peaks disappear and the parent phase undergoes a martensitic transformation. It is suggested that the parent phase undergoes a process of phase separation through the mechanism of spinodal decomposition before the martensitic transformation occurs. The martensitic transformation shows isothermal kinetics for which a transformation diagram is presented. Prolonged aging results in the formation of equilibrium phases.

Characterization of the Phase Transformations in the Shape Memory Alloy Ni-36 at.% Al

1991 ◽  
Vol 246 ◽  
Author(s):  
J.A. Horton ◽  
E.P. George ◽  
C.J. Sparks ◽  
M.Y. Kao ◽  
O.B. Cavin ◽  
...  
Keyword(s):  
High Temperature ◽  
Shape Memory ◽  
Phase Transformations ◽  
Hot Extrusion ◽  
Exothermic Peak ◽  
Nickel Aluminum ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Transmission Electron

AbstractA survey by differential scanning calorimetry (DSC) and recovery during heating of indentations on a series of nickel-aluminum alloys showed that the Ni-36 at.% Al composition has the best potential for a recoverable shape memory effect at temperatures above 100°C. The phase transformations were studied by high temperature transmission electron microscopy (TEM) and by high temperature x-ray diffraction (HTXRD). Quenching from 1200°C resulted in a single phase, fully martensitic structure. The initial quenched-in martensites were found by both TEM and X-ray diffraction to consist of primarily a body centered tetragonal (bct) phase with some body centered orthorhombic (bco) phase present. On the first heating cycle, DSC showed an endothermic peak at 121°C and an exothermic peak at 289°C, and upon cooling a martensite exothermic peak at 115° C. Upon subsequent cycles the 289°C peak disappeared. High temperature X-ray diffraction, with a heating rate of 2°C/min, showed the expected transformation of bct phase to B2 between 100 and 200°C, however the bco phase remained intact. At 400 to 450°C the B2 phase transformed to Ni2Al and Ni5Al3. During TEM heating experiments a dislocation-free martensite transformed reversibly to B2 at temperatures less than 150°C. At higher temperatures (nearly 600°C) 1/3, 1/3, 1/3 reflections from an ω-like phase formed. Upon cooling, the 1/3, 1/3, 1/3 reflections disappeared and a more complicated martensite resulted. Boron additions suppressed intergranular fracture and, as expected, resulted in no ductility improvements. Boron additions and/or hot extrusion encouraged the formation of a superordered bct structure with 1/2, 1/2, 0 reflections.

β Stability and Mechanical Behavior of Metastable β Type TiNb Based Alloys

2013 ◽  
Vol 747-748 ◽  
pp. 941-946
Author(s):  
Guang Yue Liao ◽  
Shun Guo ◽  
Zhen Zhen Bao ◽  
Xin Qing Zhao
Keyword(s):  
Martensitic Transformation ◽  
Mechanical Behavior ◽  
Microstructural Evolution ◽  
Mechanical Test ◽  
Cold Deformation ◽  
Strengthening Mechanism ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Low Elastic Modulus

Metastable β type TiNb based alloys of Ti-35Nb, Ti-35Nb-4Sn and Ti-42Nb-4Sn (wt. %) with different stability were prepared and thermo-mechanical treatment was carried out to investigate their microstructural evolution and mechanical properties. It was found that although the TiNb based alloy with lower stability performs lower strength in its solution state due to the stress induced martensitic transformation, they could be strengthened significantly by severe cold rolling followed by aging, remaining a relative low elastic modulus. X-ray diffraction, transmission electron microscopy and mechanical test were conducted to characterize the microstructural evolution and mechanical behavior of the metastable β type TiNb based alloys with different β stability. The strengthening mechanism was discussed on the basis of the cold deformation and martensitic transformation.

Fullerene-Metal Composites: Phase Transformations During Milling and Sintering

2011 ◽  
Vol 172-174 ◽  
pp. 727-732 ◽  
Author(s):  
Ileana Irais Santana ◽  
Francisco Carlos Robles Hernandez ◽  
Vicente Garibay-Febles ◽  
Hector A. Calderon
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Phase Transformations ◽  
Mechanical Milling ◽  
X Ray Diffraction ◽  
Metal Composites ◽  
X Ray ◽  
Plasma Sintering ◽  
Transmission Electron ◽  
Spark Plasma

Composites of Fe-C60and Al C60produced by mechanical milling and sinterized by Spark Plasma Sintering are investigated with special attention to the mechanical properties of the products. The processing involves phase transformations of the fullerenes that are interesting to follow and characterize. This involves formation of tetragonal/rhombohedral diamond and carbides during sintering and milling. Transmission Electron Microscopy (TEM) and Raman Spectroscopy techniques are also used to confirm preliminary results of X Ray Diffraction (XRD) related to the formation of nanostructures i.e., grain size of the crystals during mechanical milling and after sintering, spatial distribution of phases and the different phases that are developed during processing.

Understanding Precursor Phenomena for the R-Phase Transformation in Ti-Ni-Based Alloys

MRS Bulletin ◽  
2002 ◽  
Vol 27 (2) ◽  
pp. 121-127 ◽  
Author(s):  
Daisuke Shindo ◽  
Yasukazu Murakami ◽  
Takuya Ohba
Keyword(s):  
Phase Transformation ◽  
Diffuse Scattering ◽  
Parent Phase ◽  
Martensitic Transformations ◽  
X Ray Diffraction ◽  
X Ray ◽  
Atomic Displacements ◽  
Transmission Electron ◽  
Critical Issues ◽  
Structural Modulation

AbstractPrecursor phenomena are critical issues for martensitic transformations. In this article, we show recent progress in understanding precursor phenomena to the R-phase transformation, which is important for both fundamentals and applications. Structural modulation in the parent phase was intensively studied by means of detailed analyses of the weak diffuse scattering of electrons with the aid of recently developed energy-filtered transmission electron microscopy coupled with x-ray diffraction. A peculiar domain-like structure, which originates from static transverse atomic displacements in the parent phase, was discovered by virtue of these advanced methods. The characteristics of this structure (e.g., size, shape, and temperature-dependence), as well as its role in the subsequent R-phase transformation, are discussed.

Stressed In Situ X-Ray Diffraction Studies of a Ni-Ti Shape Memory Alloy

1992 ◽  
Vol 276 ◽  
Author(s):  
J. Y. Hwang ◽  
C. F. Yang
Keyword(s):  
Phase Transformations ◽  
Parent Phase ◽  
Uniaxial Tensile ◽  
Ti Alloy ◽  
Sample Holder ◽  
X Ray Diffraction ◽  
X Ray ◽  
Tensile Stresses ◽  
Quantitative Analyses

ABSTRACTThe B2 ⌊ R ⌊ B19′ phase transformations in a Ni-50.7 at.% Ti alloy were investigated under a series of uniaxial tensile stresses. A custom-build X-ray sample holder with hot, cold and stressing stages was used for structure analysis at temperatures up to 140 °C under a variety of tensile stresses (up to 250 MPa). Reorientation and growth of favorably oriented variant domains of R phase and martensite under stress were observed. In the stress-assisted phase transformations, the favorable (020)M and (300)R planes are expected to align preferably parallel to (011)B2 planes, and the unfavorable (111)M and (112)R planes perpendicular to the (011)B2 planes. In addition, the results of semi-quantitative analyses of the relative amounts of parent phase and martensite formed under a specific stress and temperature condition, x=x(σ,T), are presented.

Phase Transformation in Binary Titanium-Base Alloys with Metals of the I, IV−VIII Groups

2007 ◽  
Vol 546-549 ◽  
pp. 1349-1354 ◽  
Author(s):  
A.V. Dobromyslov
Keyword(s):  
Electron Microscopy ◽  
Structural Information ◽  
Eutectoid Decomposition ◽  
X Ray Diffraction ◽  
Minimum Concentration ◽  
X Ray ◽  
Β Phase ◽  
Ω Phase ◽  
Α Phase ◽  
Transmission Electron

Martensitic β→α′(α″) transformation, β→ω transformation and eutectoid decomposition in a series of Ti-base alloys with d transition metals of Groups I, IV-VIII have been investigated using the techniques of X-ray diffraction, optical and transmission electron microscopy. Phase and structural information is given on the non-equilibrium and metastable modifications occurring in these alloys after quenching from high-temperature β-field and aging. The conditions of the orthorhombic α″-phase, ω-phase and metastable β-phase formation in binary titanium–base alloys with d-metals of V-VIII groups were investigated. It was established that the position of the alloying metal in the Periodic Table defines the presence or absence of the α″-phase in the alloy after quenching and the minimum concentration of the alloying metal necessary for formation of the α″-phase, ω-phase and metastable β-phase.

Microstructure and Properties of Native Insulators Formed on Single Crystal Germanium

1985 ◽  
Vol 54 ◽  
Author(s):  
O. J. Gregory ◽  
E. E. Crisman ◽  
J. Severns ◽  
P. J. Stiles
Keyword(s):  
Photoelectron Spectroscopy ◽  
Hexagonal Phase ◽  
Far Infrared ◽  
Infrared Transmission ◽  
X Ray Diffraction ◽  
X Ray ◽  
Native Oxides ◽  
Β Phase ◽  
Transmission Electron ◽  
Scanning Transmission

ABSTRACTThe phases, morphologies and microstructures of native oxides and nitrides, grown on the vicinal planes of germanium, are discussed. Thermal oxides, formed under high pressure, were shown to be primarily amorphous for (100) and (110) oriented substrates and intermixed with a crystalline hexagonal phase on the (111) surfaces. Thermal treatments, in one atmosphere of flowing ammonia gas, converted oxide films to mixtures of nitrides and oxynitrides with the nitrides found to be combinations of a- and β-Ge3N4. The α-phase formed from condensation of vapors above the surface whereas the β-phase was a solid-solid reaction product which initiates at the oxide/germanium interface. These two processes appeared to proceed independently of each other. Results of low angle X-ray diffraction (XRD), far infrared transmission (FIRT), scanning transmission electron microscopy (STEM) and X-ray photoelectron spectroscopy (XPS) are discussed.

Martensitic Transformation of TiAu Shape Memory Alloys

2007 ◽  
Vol 561-565 ◽  
pp. 1541-1544 ◽  
Author(s):  
Hideki Hosoda ◽  
Ryosuke Tachi ◽  
Tomonari Inamura ◽  
Kenji Wakashima ◽  
Shuichi Miyazaki
Keyword(s):  
Martensitic Transformation ◽  
Shape Memory ◽  
Parent Phase ◽  
Stoichiometric Composition ◽  
Transformation Strain ◽  
Martensite Phase ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Rich Side

Martensitic transformation temperatures were measured and transformation strains were evaluated in a promising high temperature shape memory alloy TiAu with a compositional range from 46 to 53mol%Au. It was found by differential scanning calorimetry that martensitic transformation start temperature (Ms) is kept almost constant value of 880K in the Au-rich side of the stoichiometric composition. On the other hand, Ms decreases monotonically with decreasing Au content in the Au-poor side. X-ray diffraction analysis revealed that apparent phase of all the alloys at room temperature is B19 martensite phase. Under an assumption that the atomic volume is constant during martensitic transformation, the lattice parameters of B2 parent phase and maximum transformation strain were calculated. It was found that the maximum transformation strain depends on chemical composition and that it reaches 10.75% for Ti-53mol%Au alloy. The value is comparable to that of Ti-Ni.

Microstructures of Fe-Pd Alloy Ribbons Subjected to Rapidly Solidified Melt Spinning

2013 ◽  
Vol 738-739 ◽  
pp. 431-435
Author(s):  
Yoichi Kishi ◽  
Takeshi Kubota ◽  
Zenjiro Yajima ◽  
Teiko Okazaki ◽  
Yasubumi Furuya ◽  
...  
Keyword(s):  
Pole Figure ◽  
Melt Spinning ◽  
Room Temperature ◽  
Parent Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Oriented Texture ◽  
Pd Alloy ◽  
Rapidly Solidified

Microstructures of the Fe-29.6at%Pd alloy ribbons were observed with an X-ray diffractometer and a transmission electron microscope. The X-ray diffraction profiles at room temperature showed that the ribbon consists of FCT martensitic phase and FCC parent phase. Moreover, the ribbon exhibits a strongly 200-oriented texture analyzing with pole figure measurements. TEM bright field images for the cross section of the ribbon showed high-density striation in the FCT martensite variants. Twin-related two sets of reflections were observed in the SAED patterns taken of the FCT martensite variants. FCT was nearly parallel to the thickness direction according to the analysis of the SAED patterns. This result corresponds to the pole figure measurements.

scholarly journals Solid-State Phase Transformations in Thermally Treated Ti–6Al–4V Alloy Fabricated via Laser Powder Bed Fusion

Materials ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 2876
Author(s):  
Paolo Mengucci ◽  
Eleonora Santecchia ◽  
Andrea Gatto ◽  
Elena Bassoli ◽  
Antonella Sola ◽  
...  
Keyword(s):  
Solid State ◽  
Phase Transformations ◽  
Xrd Analysis ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
X Ray Diffraction ◽  
Powder Bed ◽  
Β Phase ◽  
Transmission Electron ◽  
Scanning Transmission

Laser Powder Bed Fusion (LPBF) technology was used to produce samples based on the Ti–6Al–4V alloy for biomedical applications. Solid-state phase transformations induced by thermal treatments were studied by neutron diffraction (ND), X-ray diffraction (XRD), scanning transmission electron microscopy (STEM) and energy-dispersive spectroscopy (EDS). Although, ND analysis is rather uncommon in such studies, this technique allowed evidencing the presence of retained β in α’ martensite of the as-produced (#AP) sample. The retained β was not detectable by XRD analysis, nor by STEM observations. Martensite contains a high number of defects, mainly dislocations, that anneal during the thermal treatment. Element diffusion and partitioning are the main mechanisms in the α ↔ β transformation that causes lattice expansion during heating and determines the final shape and size of phases. The retained β phase plays a key role in the α’ → β transformation kinetics.

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